Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.73	9.835%	$123.817	$123.82	$123.80	$123.80
Purchase #2	$73.83	5.717%	$78.0509	$78.05	$78.05	$78.10
Purchase #3	$74.52	7.719%	$80.2722	$80.27	$80.25	$80.30
Purchase #4	$219.80	3.718%	$227.9722	$227.97	$227.95	$228.00
Purchase #5	$143.82	8.327%	$155.7959	$155.80	$155.80	$155.80
Purchase #6	$137.59	3.179%	$141.964	$141.96	$141.95	$142.00
Purchase #7	$92.60	9.486%	$101.384	$101.38	$101.40	$101.40
7 purchase totals =	$854.89		$909.2562	$909.25	$909.20	$909.40